Foreword by Ian Thompson, Editor
Welcome to our latest Build Review video post where we continue to delve into the ever evolving world of renewable energy, specifically focusing on the potential of wind turbines for home use. We’ve all seen the large-scale wind turbines dotting the landscape, harnessing the power of the wind for grid scale renewable energy. Solar power has also made a significant impact, with panels now a common sight on many homes, including my own. But what if we could scale down those giant wind turbines and install them on our houses, making use of the wind particularly on windy overcast days? Could this be a viable alternative or supplement to solar power? This video takes a deep dive into the potential of micro wind turbines, comparing them with solar panels to determine which is the most practical and efficient for home use.
We will also explore the various technologies and innovations in this space, and discuss the pros and cons of choosing wind power for your home. Over to one of our regular American authors Matt Ferrell:
The Challenges of a Wind Turbine on Your Home
We’ve seen wind turbines popping up everywhere in the last few years for grid scale renewable energy installations. Solar panels for home has been a disruptive technology, but what if we could scale down wind turbines and install them on our home? In theory it sounds like a good idea to diversify our home power generation, but does it make sense to install micro wind turbines on your home vs. just installing solar panels? Let’s see if we can come to a decision on this.
We’ve seen wind turbines popping up everywhere in the last few years, though these are mostly grid scale installations. For at-home power generation solar power has been a disruptive technology, but what if we could scale down wind turbines and install them on our roofs? What would happen if we could install a wall of wind turbines outside? In theory it sounds like a good idea to diversify our home power generation, but does it make sense to install micro wind turbines on your home vs. just installing solar panels? Let’s see if we can come to a decision on this.
I’ve had solar panels on my roof for a little over 3 years now, but I’ve always been fascinated by wind turbines. However, it just doesn’t make sense for my home in my location, but in the abstract it makes sense to diversify your energy sources to give yourself more resilience and independence. For instance, your wind turbine could still be generating power in the middle of the night when your solar panels aren’t, so they sound like a good compliment for each other. And a lot of you have mentioned the same thing in the comments, asking about adding wind turbines to your home, but it’s not exactly a rosy picture … for your home that is.
When looking at greener technologies that can get us the power we need without the carbon emissions, wind is gaining in popularity around the world. This popularity boost is due in part to the falling prices. From 2019 to 2020, wind-generated electricity increased by 170 TWh (terawatt-hour), which is an 11% boost in just one year. If we take hydropower out of the picture, wind power becomes the most impactful renewable energy source used around the globe, generating 1,592 TWh of clean electricity every year. 1 Again though, that’s almost completely at grid scale.
When it comes to Levelized Costs of Electricity, the Annual Energy Outlook 2021 developed by the U.S. Energy Information Administration (EIA) shows that wind power costs about US$31.45/MWh, which is pretty competitive to the US$31.30/MWh for standalone solar. 2 Unlike wind, solar has been widely used at small-scale installations, like on homes. My tiny house is definitely a “small-scale installation.”3 4
The obvious question is why not scale down wind turbines, so they could also be installed on our homes? There are several companies trying to make that happen, but before we get to those, let’s take a closer look at the basics of how conventional wind turbines work, which kind of illustrates the challenges.
Usually, wind turbines have huge rotor blades (usually around 50 meters). The key here is that the longer the rotor blades, the more energy the wind turbine can generate from the same wind speed. That means a micro-sized turbine is going to generate far less energy than a massive turbine from the same wind speed. As the blades spin, the captured kinetic energy turns the turbines’ rotor, which generates the electricity
In large-scale wind turbines, which are generating power in the MW scale, there’s a pitch control mechanism in the front side that adjusts the blades’ angle in order to harvest more energy. Then inside the nacelle (the main body sitting on top of the tower) there’s a gearbox that converts the low-speed rotation of the blades into higher-speed in order to drive the generator efficiently. There’s also rotor brakes for safety reasons, an anemometer for measuring wind, and a yaw control system that controls the horizontal orientation of the turbine. All of these systems work together to optimize performance and to keep the turbine from destroying itself. It’s a whole lot of moving parts.
That’s at the large scale, so how do the scaled down models fare? Micro wind turbines typically produce between 400W-500W, but they can go up to 10kW-20kW depending on the application. Their blades are often 1.5 to 3.5 meters in diameter and made of synthetic materials like carbon fiber reinforced polymers to make them strong and lightweight. While large-scale wind turbines have active yaw systems and electronic pitch control, small wind turbines utilize passive yaw systems and mechanical pitch control, or even no pitch control at all. They’re far more simplified, but still have moving parts (this theme will keep coming up).
Depending on the model, small wind turbines usually can produce either direct current (DC) or alternate current (AC). Just like solar panels on your home, with DC generation, you’d need to install a DC-AC inverter to make use of the power for standard AC outlets and appliances around your home. Adding power conversion in the system reduces the overall efficiency. It’s a minor downside, but worth noting.
Wind generators are classified into three types, regardless of whether they are large or small scale. Horizontal-axis turbines are the most common type and they’re probably what you picture in your head when it comes to wind power. They operate horizontally, turning at the top of the tower so that the blades face the wind. Another type is vertical-axis turbines, which are perpendicular to the ground and can be powered by the wind coming from any direction, even from top to bottom. There are also solid-state wind turbines with no moving parts, which I explored in a previous video if you want to deep dive into that technology. Those are still off in the future.
At a high level, small wind turbines sound like a great option to decarbonize homes. Just like adding solar panels to your home, you might be able to sell your excess power generation to your utility, generating credits for yourself. The installation may also qualify for tax incentives at the local or national level, but of course, you’d have to look into that for your specific area. Ultimately, the motivating reasons for installing wind turbines on your home are really no different than adding solar panels: generate your own energy, reduce your dependence on fossil fuels, and avoid the issues of increasing energy prices over time.
However, there are several cons we have to consider.
First, the wind doesn’t blow all the time (again, obviously), so micro wind turbines operate around 30-40% of their capacity. If the turbines are installed on a rooftop, they can vibrate, resulting in noise and potential structural issues. The noise coming from the blades (even in small wind turbines) can be in the range of 50 to 60 decibels. All of this ties back to the moving parts theme.
There’s also the height to consider. The recommended average height of a small wind turbine is 65 feet, which is pretty high up there. Anything lower than that could be affected by nearby buildings or trees that disrupt the wind’s smooth path. On top of that, many housing developments won’t allow such tall structures to be built. Wind power makes more sense in more rural locations, where neither of these points are an issue.
Unstable wind flow can cause turbulence, stressing the turbine elements and may affect the wind measurement from the anemometer. This can lead to safety issues, since the control system will make inappropriate decisions based on the incorrect wind speed.12 13 14 “Inappropriate decisions” sounds like my college years.
There’s also the operation and maintenance costs to consider. Modern turbines have a maintenance cost ranging from 1.5% to 2% of their original cost per year. If you bought a residential wind turbine for $8000, you can expect to spend about $120-$160 per year to maintain your turbine with regular servicing including oil, greases and filters, as well as mechanical and electrical checks.15 16 Again, moving parts. Compare that to solar, which is essentially maintenance free since there’s no moving parts.
Speaking of costs, the cost of a small wind turbine for a home or a small business ranges from $3,000 to $8,000 per kW installed. A 10kW wind turbine installation for a large house costs from $50,000 to $80,000. 14 Comparatively, the same 10 kW installation using solar panels currently costs $20,498 on average here in the US. That’s about a $2,950 difference per kW install … and that’s not even counting the current 26% Federal solar tax credit that brings the solar cost per kW even lower.17 18
Now, I live in Massachusetts, so let’s use my area as a theoretical installation. We’ll be installing a 1 kW wind turbine, which will experience an average wind speed of about 4 m/s. That means this conventional 1kW wind turbine will produce about 100W – only 10% of its rated capacity at that speed. So, in one year, considering the average wind speed in Massachusetts, this turbine would produce about 876 kWh. My cost for electricity is usually around $0.25/kWh, so this turbine would save about $219 in one year. If we consider that the cost of installing a 1 kW turbine would be about $5,000, this would result in a payback period of 22 years.
On the flip side, with average peak sun hours of 4.2 hours in Massachusetts, an equivalent 1kW solar panel system would produce 4.2kWh a day, and 1,533 kWh in one year at an average cost of $2,770. So this system would save $383.25 per year in electricity and the payback period would be about 7 years. 19
Sounds pretty damning for my area, but wind is still one of the greenest power sources, producing only 4 grams of CO2 per kWh, which is slightly better than solar at 6 grams. Both of those are dramatically better than gas at 78 grams or coal at 109 grams. That’s one of the reasons that many companies around the globe have been trying out innovative designs and technologies to make wind turbines more feasible for homeowners.
One company manufacturing vertical axis turbines, which we have already explored in my solid-state wind energy video, is Icewind. They offer two models for pre-order, CW100 for residential applications and RW100 for industrial applications. The cost of the 600W residential wind turbine is $3,200 including the support structure, but a complete on-grid system with a 1.5kW inverter would cost about $4,150.20
Another direction is the Archimedes windmill developed by the Dutch company KETech. This turbine consists of three circular blades that are wrapped around each other and then enlarged, making it look like a rose. The Archimedes windmill captures about 35% of all kinetic energy, is fairly silent, generating less than 45dB, and can generate electricity with wind speeds as low as 0.9m/s, which is very low compared to other models on the market. Because of its conical shape, the wind turbine yaws itself automatically to sit at the best angle to harness the wind. The company is developing two models that can produce between 150W and 1000W, but they’re still at the development stage. While promising, these designs are not yet for sale. According to the company, the 1 kW turbine can produce 1,500 kWh in one year at wind speeds of 5 m/s. That would be an improvement over my theoretical installation I talked about a minute ago.
What if you don’t want a giant fan hovering over your house? You might want to look at something like the RidgeBlade® wind turbine, which is manufactured by the Ontario-based company The Power Collective. Their technology takes advantage of the Aeolian wind focus effect, where the wind is forced to travel over the roof surface, forming a pinch point at the roof ridge, which speeds up the airflow through the turbine by about 3 times at optimal roof pitch angles. According to the company, when installed in places with high airflow, the RidgeBlade® can produce up to nine times the energy of a traditional horizontal axis wind turbine. It achieves its full capacity with wind speeds of 11 m/s, but has been tested against more than 40 m/s. 25 It can operate with 100% performance from 0º to 45º in a bidirectional way, can withstand turbulent air conditions commonly found in urban environments, and is quiet and vibration-free. 26
The blades self-regulate and the spacing between them results in flow separation and torque loss at high wind speeds, so the system doesn’t require external or other mechanical braking systems. The ability to protect itself during high wind events, such as storms, is an important feature.
Their RB1 Residential can produce 2 kW of clean power or 2.7 kW peak. Over the course of a year it’s capable of producing 5,000 kWh at 6 m/s average wind speed and installed on a roof with a 40º slope. 27 28 29 Although this technology is very interesting, we couldn’t get information on prices or installations using this tech.
If you want to really push the boundaries, the designer Joe Doucet created the Wind Turbine Wall. It’s built out of 25 wind turbine generators with the blades spinning in the middle. The wall is 8 feet (2.4 meters) tall and 25 feet (7.6 meters) wide and can produce up to 10kW, but the design can be customized for each customer. The turbines will operate at around 35% capacity, which is the average for US land-based horizontal wind turbines. That means you’d get around 84 kWh a day. Although it looks cool, this technology is still in the concept phase and probably won’t produce a great amount of energy in an urban environment. The sheer size of the turbine also limits its application.
While each of these are promising technologies, some of these concepts still haven’t hit the market for sale. When you’re looking at the outlook for the micro wind turbine sector, it’s clear there’s not a super positive outlook here. The small wind turbine market was valued at $277.4 million in 2020 and is expected to grow at a CAGR of 1.4% between 2022-2027, reaching $310 million. That’s extremely small compared to the solar panel market, which was valued at $170.55 billion in 2020, and it’s expected to reach $293.18 billion in 2028, growing at a CAGR of 6.9% from 2021 to 2028. 31 32
With all of that, it sounds like adding wind to your home today just doesn’t make sense, but it does depend on your goals and where you live. If you’re building an off-grid home in an area with a lot of wind it may make sense to diversify your energy generation between solar and wind. But for the rest of us? It’s cheaper and easier to add a few extra panels onto our roof and call it a day. Low capacity and high costs result in long payback periods for the models currently available on the market, which makes solar the most cost effective and low maintenance solution for homeowners. Alternatives to increase power capacity and aesthetics, like the RidgeBlade, aren’t widely available in all areas yet. After all of this, my final decision is that, for right now, wind power is still a very limited choice for home installations, especially compared to solar, which has proven to be a very effective solution for homes.
External Youtube related post: How do Wind Turbines work?